[Desktop_printing] PPD settings vs IPP options

[Alexander Larsson]

I'm starting to look at the Gtk+ print dialog, and I have some questions
about how things are supposed to work.

When the user pops up the print dialog, with some printer selected the
UI is modified to the capabilities of that printer (set of input trays,
paper sizes, etc), and the defaults are set up according to some
defaults set for the printer. We then let the user select their options,
create a postscript file and send it to the printer.

Now, there seems to be two ways of doing this. Either using PPDs, or
using IPP options:

1) Get the PPD file for the printer, use the PPD file to set up the UI
and defaults. When printing, embed the postscript snippets from the PPD
file based on the settings the user made. Send this to the cups/ipp
server.

2) Get IPP attributes for the cups printer (media-supported,
media-default, orientation-requested-supported,
orientation-requested-default, etc). Use this info to set up the UI, and
defaults. When printing create a "plain" postscript file, and pass this
to cups/ipp together with a set of ipp options based on what the user
selected in the UI.

Is one way preferable over the other in any way? Does it ever make sense
to mix these different methods?

It seems to me that using the PPD file allows higher fidelity in the UI
(with UIConstraints and things like that) and allows printer-specific
features. So, IMHO it looks like a better choice, but I don't know all
the details here.

The PPD method only seems to work if you use postscript files though.
How would this work if we used e.g. PDF as the spool format?

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 Alexander Larsson                                            Red Hat, Inc 
                   alexl at redhat.com    alla at lysator.liu.se 
He's a fast talking overambitious assassin on a search for his missing sister. 
She's a high-kicking winged cab driver with an MBA from Harvard. They fight 
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